Optimized outer clutch housing for reduced spin loss, improved oil flow and improved clutch durability

ABSTRACT

A torque transfer device can include a housing and a clutch. The housing can define a clutch cavity and a pocket. The pocket can be formed at an axial end of the clutch cavity and have a generally arcuate shape that extends circumferentially about the clutch cavity above a static lubrication level. The clutch can include an outer carrier, an inner carrier, a plurality of first and second interleaved friction plates. One of an outer and an inner plate carrier of the clutch can be coupled to an input member for common rotation. The other of the carriers can be coupled to a differential case for common rotation. Rotation of the outer carrier relative to the housing through a fluid in the clutch cavity can sling a portion of the fluid toward an inner surface of the housing to cause the portion of the fluid to collect in the pocket.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/460,597, filed Aug. 15, 2014, which claims the benefit of U.S.Provisional Application No. 61/869,359, filed on Aug. 23, 2013. Theentire disclosure of the above application is incorporated herein byreference.

FIELD

The present disclosure relates to power transmitting components havingan optimized outer clutch housing for reduced spin loss, improved oilflow and improved clutch durability.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Power transmitting components with a torque transfer device, such as adisconnecting drive module in an all wheel drive (“AWD”) system, caninclude a clutch with a plurality of friction plates and a piston forselectively driving the friction plates into engagement with oneanother. The friction plates are generally bathed in a fluid to providelubrication and cooling of the friction plates when the clutch isengaged. When the clutch is disengaged, fluid between the frictionplates and within a clutch sump through which the friction plates rotatecan undesirably increase the system drag torque. To reduce the magnitudeof the system drag torque, the level of fluid within the clutch sumpcould be reduced. However, sufficient fluid must be available duringengagement of the clutch to ensure that the clutch will not experiencepremature wear.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present teachings provide for a torque transfer device including ahousing, an input pinion, an input member, a first output member, asecond output member, a differential, a shaft, a fluid, and a frictionclutch. The housing can define a clutch cavity and a pocket. The pocketcan be formed at an axial end of the clutch cavity and can have agenerally arcuate shape that can extend circumferentially about theclutch cavity and can be above a static lubrication level when thetorque transfer device is disposed in a predetermined orientation. Theinput pinion can be configured for rotation about a first axis. Theinput member can be configured for rotation about a second axis and canbe meshingly engaged with the input pinion. The differential can includea differential case and a differential gearset. The differential gearsetcan be configured to transmit rotary power between the differential caseand the first and second output members. The shaft can be supportedwithin the housing for rotation about the second axis and can be coupledfor common rotation with the differential case. The fluid can bereceived in the clutch cavity. The friction clutch can include an outercarrier, an inner carrier, a plurality of first friction plates, and aplurality of second friction plates. The outer carrier can have a firstplate mount onto which the first friction plates are non-rotatablymounted. The inner carrier can have a second plate mount onto which thesecond friction plates are non-rotatably mounted. The second frictionplates can be interleaved with the first friction plates. One of theouter and inner carriers can be coupled to the shaft for commonrotation. The other of the outer and inner carriers can be coupled tothe input member for common rotation. Rotation of the outer carrierrelative to the housing in a predetermined rotational direction throughthe fluid in the clutch cavity can sling a portion of the fluid towardan inner surface of the housing to cause the portion of the fluid tocollect in the pocket.

The present teachings further provide for a torque transfer deviceincluding a housing, an input pinion, an input member, a first outputmember, a second output member, a differential, a shaft, and a frictionclutch. The housing can have a circumferential wall and a pair of endwalls. The circumferential wall can extend circumferentially about anaxis. The end walls can be located at opposite axial ends of thecircumferential wall. The circumferential wall and pair of end walls candefine a clutch cavity. The input pinion can be configured for rotationabout a first axis. The input member can be configured for rotationabout a second axis and can be meshingly engaged with the input pinion.The differential can include a differential case and a differentialgearset. The differential gearset can be configured to transmit rotarypower between the differential case and the first and second outputmembers. The shaft can be supported within the housing for rotationabout the second axis and can be coupled for common rotation with thedifferential case. The friction clutch can include an outer carrier, aninner carrier, a plurality of first friction plates, and a plurality ofsecond friction plates. The outer carrier can have a first plate mountonto which the first friction plates are non-rotatably mounted. Theinner carrier can have a second plate mount onto which the secondfriction plates are non-rotatably mounted. The second friction platescan be interleaved with the first friction plates and can be configuredto transmit rotational power between the shaft and the input member. Oneof the end walls can define a pocket proximate to the circumferentialwall. The pocket can extend about a portion of the circumference of theone of the end walls and above a static lubrication level when thetorque transfer device is disposed in a predetermined orientation and apredetermined volume of a fluid is received in the clutch cavity.Rotation of the outer carrier relative to the housing in a predeterminedrotational direction through the fluid in the clutch cavity can sling aportion of the fluid toward an inner surface of the housing to cause theportion of the fluid to be retained by the pocket.

The present teachings further provide for a torque transfer deviceincluding an input pinion, an input member, a first output member, asecond output member, a differential, a housing, a lubricant fluid, afirst shaft, a bearing, and a friction clutch. The input pinion can beconfigured for rotation about a first axis. The input member can beconfigured for rotation about a second axis and can be meshingly engagedwith the input pinion. The differential can include a differential caseand a differential gearset. The differential gearset can be configuredto transmit rotary power between the differential case and the first andsecond output members. The housing can define a clutch cavity and apocket. The pocket can be formed at an axial end of the clutch cavityand can extend circumferentially above a static lubrication level whenthe torque transfer device is disposed in a predetermined orientation.The lubricant fluid can be received in the clutch cavity. The firstshaft can be disposed in the clutch cavity and can be coupled for commonrotation with the differential case. The bearing can be disposed betweenthe shaft and the housing. The friction clutch can include an outerclutch plate carrier, an inner clutch plate carrier, a plurality offirst friction plates, and a plurality of second friction plates. Theouter clutch plate carrier can have a first plate mount onto which thefirst friction plates are axially slidably but non-rotatably mounted.The inner clutch plate carrier can have a second plate mount onto whichthe second friction plates are axially slidably but non-rotatablymounted. The second friction plates can be interleaved with the firstfriction plates and can be configured to transmit rotational powerbetween the shaft and the input member. The outer clutch plate carrierand the housing can define a radial space disposed between the outerclutch plate carrier and the housing. The radial space can extend in anaxial direction along a rotational axis of the outer clutch platecarrier. The radial space can intersect the pocket and be sized so thatlubricant fluid slung from the outer clutch plate carrier can bedirected axially along the housing to the pocket. The pocket can includea first lubricant feed gallery that can be configured to directlubricant from the pocket to one of the bearing to lubricate thebearing, and an orifice through the second plate mount to lubricate thefirst and second clutch plates.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic illustration of an exemplary vehicle having apower transmitting component constructed in accordance with the presentteachings;

FIG. 2 is a perspective view of the power transmitting component of FIG.1;

FIG. 3 is a cross-sectional view of the power transmitting unit of FIG.2 taken along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional perspective view of a portion of the powertransmitting component of FIG. 1 taken along line 4-4 of FIG. 2,illustrating a clutch having a clutch housing for reduced spin loss;

FIG. 5 is a side elevation view of a portion of the clutch housing ofFIG. 4;

FIG. 6 is a cross-sectional view of the clutch of FIG. 4 taken alongline 6-6 of FIG. 2, illustrating a location of a lubricant fluid whenthe vehicle is at rest; and

FIG. 7 is a cross-sectional view of the clutch of FIG. 4 taken alongline 7-7 of FIG. 2, illustrating a location of a lubricant fluid whenthe vehicle is moving and the clutch is in a first state.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With reference to FIG. 1 of the drawings, an exemplary vehicle having apower transmitting component constructed in accordance with theteachings of the present disclosure is generally indicated by referencenumeral 10. The vehicle 10 can have a power train 12 and a drive line ordrive train 14. The power train 12 can be conventionally constructed andcan comprise a power source 16 and a transmission 18. The power source16 can be configured to provide propulsive power and can comprise aninternal combustion engine and/or an electric motor, for example. Thetransmission 18 can receive propulsive power from the power source 16and can output power to the drive train 14. The transmission 18 can havea plurality of automatically or manually-selected gear ratios. The drivetrain 14 in the particular example provided is of an all-wheel driveconfiguration, but those of skill in the art will appreciate that theteachings of the present disclosure are applicable to other drive trainconfigurations, including four-wheel drive configurations, rear-wheeldrive configurations, and front-wheel drive configurations. The drivetrain 14 can include a front axle assembly 20, a power take-off unit(PTU) 22, a prop shaft 24 and a rear axle assembly 26. The front axleassembly 20 can be configured in any desired manner, such as a fronttransaxle, a front beam axle, or an independent front drive axle. Anoutput of the transmission 18 can be coupled to an input of the frontaxle assembly 20 to drive an input member 30 of the front axle assembly20. The PTU 22 can have a PTU input member 32, which can receive rotarypower from the input member 30 of the front axle assembly 20, and a PTUoutput member 34 that can transmit rotary power to the prop shaft 24.The prop shaft 24 can couple the PTU output member 34 to the rear axleassembly 26 such that rotary power output by the PTU 22 is received bythe rear axle assembly 26. The rear axle assembly 26 can be configuredin any desired manner, such as a rear beam axle, an independent reardrive axle, or a rear drive module. The front axle assembly 20 and therear axle assembly 26 can be driven on a full-time basis to drive frontand rear vehicle wheels 40 and 42, respectively. Alternatively, thedrive train 14 can include one or more clutches to interrupt thetransmission of rotary power through a part of the drive train 14. Inthe particular example provided, the drive train 14 includes a firstclutch 46, which can be configured to interrupt the transmission ofrotary power through the PTU 22 (e.g., decouple the input member 30 ofthe front axle assembly 20 from the PTU input member 32), and a secondclutch 48, which can be configured to control rotation of componentswithin the rear axle assembly 26.

In the particular example provided, the rear axle assembly 26 includes arear drive module 50 (i.e., a power transmitting component) that isconstructed in accordance with the teachings of the present disclosure.It will be appreciated, however, that the teachings of the presentdisclosure have application to various other power transmittingcomponents, such as transmissions, power take-offs, torque transferdevices, transfer cases, front axle assemblies, center bearingassemblies for propshafts and any other power transmitting componentsthat have a housing, a shaft and a shaft seal.

With reference to FIGS. 2-4, the rear drive module 50 is illustrated inmore detail. The rear drive module 50 can include a housing 210, aninput pinion 212, an input member 214, the second clutch 48, adifferential assembly 216, and a pair of output shafts 218. The inputpinion 212, input member 214, the second clutch 48, the differentialassembly 216, and the output shafts 218 can be constructed in a mannerthat is disclosed in co-pending U.S. patent application Ser. No.13/470,941 and as such, a detailed discussion of these components is notneeded herein. Briefly, the housing 210 can define a first cavity 220and the input pinion 212 can be a hypoid pinion having a hypoid gear 222and an input pinion shaft 224. The hypoid gear 222 can be disposedwithin the first cavity 220. The input pinion shaft 224 can be supportedfor rotation in the housing 210 along a first axis 226 by a head bearing228 proximate to the hypoid gear 222 and a tail bearing 230 distal tothe hypoid gear 222 and proximate to the prop shaft 24. The input member214 can be a ring gear having a gear face 232 and an axially extendingportion 236. The axially extending portion 236 can be supported forrotation in the housing 210 about a second axis 240 by a bearing 242.The second axis 240 can be generally perpendicular to the first axis226. The gear face 232 can be meshingly engaged with the input pinion212.

The differential assembly 216 can include a differential case 244 and adifferential gearset 246. The differential case 244 can be configuredfor rotation about the second axis 240. The differential gearset 246 canbe configured to transmit rotary power between the differential case 244and the output shafts 218. In the example provided, the differentialgearset 246 includes a pair of side gears 248 and a pair of output gears250 disposed within the differential case 244. The side gears 248 can becoupled for rotation with the differential case 244 about the secondaxis 240 and coupled for rotation relative to the differential case 244about a third axis 252. The third axis 252 can be generallyperpendicular to the second axis 240. The third axis 252 can begenerally parallel with the first axis 226. The output gears 250 can bemeshingly engaged with the side gears 248 and configured to rotate aboutthe second axis 240. Each of the output shafts 218 can have a first end254, which can be drivingly coupled to a respective one of the outputgears 250, and a second, opposite end 256 that can be coupled to acorresponding one of the rear wheels 42 (FIG. 1).

The second clutch 48 can be selectively operated to transmit rotarypower from the input member 214 to the differential case 244. In theparticular example provided, the second clutch 48 is a friction clutchthat is mounted co-axially with the input member 214 and thedifferential assembly 216. The second clutch 48 can include a clutchhousing 258, an outer clutch plate carrier 260, an inner clutch platecarrier 262, a plurality of first clutch plates 264, a plurality ofsecond clutch plates 266, a piston 268, an apply plate 270, a pump 272and a pump motor 274. The clutch housing 258 can be integrally formedwith or partially formed by the housing 210 of the rear drive module 50or can be mounted to the housing 210. The clutch housing 258 can includea first side 276 and a second side 278 that can define a second cavity280 and a piston chamber 182. The first side 276 can include a wall 284that can separate the first cavity 220 from the second cavity 280. Theouter and inner clutch plate carriers 260, 262 and the first and secondclutch plates 264, 266 can be received in the second cavity 280. Aportion of the second cavity 280 can define a clutch sump S wherein alubricant fluid L (shown in FIG. 6) can collect when the outer clutchplate carrier 260 is not rotating. The second side 278 can have an outercircumferential wall 286 and a second wall 288. The outercircumferential wall 286 can define a bore 290 having an inner boresurface 292 and the second wall 288 can have an inner wall surface 294.The inner bore surface 292 and inner wall surface 294 can face generallyinward to at least partially define the second cavity 280. In theexample shown, the bore 290 is “as cast” (i.e., net shaped when cast)and is formed with draft (i.e., taper), but it should be appreciatedthat draft or tapering is not needed. Also, the amount of radial orcircumferential clearance between the outside diameter of the outerclutch plate carrier 260 and the inside diameter of the bore 290 willvary depending on various design criteria, including the outsidediameter of the outer clutch plate carrier 260.

The outer clutch plate carrier 260 can have an inner portion 296, afirst plate mount 298, and a first connecting portion 300. The innerportion can be radially inward of the first plate mount 298 andnon-rotatably coupled to the differential case 244. The plurality offirst clutch plates 264 can be non-rotatably and axially slidablycoupled to the first plate mount 298. The inner portion 296 and thefirst plate mount 298 can be fixed for common rotation by the firstconnecting portion 300. The inner clutch plate carrier 262 can have aninner portion 302, a second plate mount 304, and a second connectingportion 306. The inner portion 302 can be radially inward of the secondplate mount 304 and non-rotatably coupled to axially extending portion236 of the input member 214. The plurality of second clutch plates 266can be non-rotatably and axially slidably coupled to the second platemount 304 and interleaved with the first clutch plates 264 in a firstannular cavity 308 that is radially between the first and second platemounts 298, 304. The inner portion 302 and second plate mount 304 can befixedly coupled by the second connecting portion 306. The second platemount 304 and second connecting portion 306 of the inner clutch platecarrier 262 and the inner portion 296 and the first connecting portion300 of the outer clutch plate carrier 260 can define a second annularcavity 310 radially inward of the first annular cavity 308. The outerportion 302 of the inner clutch plate carrier 262 can further define aplurality of lubrication holes 312 extending radially outward to fluidlycouple the first and second annular cavities 308, 310. The inner portion302, second plate mount 304, and second connecting portion 306 of theinner clutch plate carrier 262 can partially define a third annularcavity 314 axially spaced apart from the second annular cavity 310 andradially inward of the first annular cavity 308. The lubrication holes312 can also fluidly couple the third annular cavity 314 with the firstannular cavity 308. The second connecting portion 306 of the innerclutch plate carrier 262 can generally be a web defining a plurality ofthrough-holes 316 fluidly coupling the second and third annular cavities310, 314. In the example provided, the through-holes 316 are tapered ina direction that diverges with increasing distance away from the firstconnecting portion 300 of the outer clutch plate carrier 260 and towardthe first side 276. The shape of the through-holes 316 may help directthe flow of lubricant fluid L through the second connecting portion 306of the inner clutch plate carrier 262. The first connecting portion 300of the outer clutch plate carrier 260 can also generally be a webdefining a plurality of through-holes 318 to allow lubricant fluid L toenter the second annular cavity 310.

The piston 268 can be received in the piston chamber 182 and configuredto translate along the second axis 240. The piston 268 can be configuredto move within the piston chamber 182 between an extended position and aretracted position relative to the plurality of first and second clutchplates 264, 266. The pump 272 can be mounted to the housing 210proximate to the pinion shaft 224 in a space generally between thehousing 210 and the clutch housing 258. The pump motor 274 can be a2-way servo motor capable of running in forward and reverse and can bedrivingly coupled to the pump 272 to selectively operate the pump 272.The pump 272 and pump motor 274 can extend radially outward from thefirst axis, generally parallel to the ground (not shown) and second axis240, and above the bottom of the housing 210 and clutch housing 258 andcan be configured to supply a hydraulic fluid to the piston chamber 182to move the piston 268 from the retracted position to the extendedposition. The pump can be configured to selectively remove hydraulicfluid from the piston chamber 182 to move the piston 268 from theextended position to the retracted position The apply plate 270 can bereceived in the second cavity 280 between the piston 268 and theplurality of first and second clutch plates 264, 266. The piston 268 canbe configured to translate the apply plate 270 along the second axis 240to selectively engage the first and second clutch plates 264, 266 tocompress the first and second clutch plates 264, 266 against one anotherso that the second clutch 48 can transmit rotary power between the inputmember 214 and the differential case 244. It will be appreciated thatthe second clutch 48 is not configured to transmit rotary power betweenthe input member 214 and the differential case 244 when the piston 268is retracted.

With additional reference to FIG. 5, the clutch housing 258 can define acircumferentially-extending oil pocket 320 that is employed to hold aportion of the lubricant fluid L in the clutch housing 258 to therebyreduce the amount of lubricant fluid L in the clutch sump S of theclutch housing 258. By reducing the amount of lubricant fluid L in theclutch sump S, the oil pocket 320 can thereby reduce the “paddlingeffect” that occurs as the outer clutch plate carrier 260 rotatesthrough the lubricant fluid L in the clutch sump S. The oil pocket 320can have a main portion 322 and a pair of ends 324, 326. The mainportion 322 and ends 324, 326 can be disposed about a portion of thecircumference of the bore 290 in the clutch housing 258 in which theouter clutch plate carrier 260 is received. The main portion 322 can bedisposed in the second wall 288 proximate to the juncture of the secondwall 288 and the inner bore surface 292. The ends 324, 326 can bedisposed above a static lubricant level 328, which is the level in theclutch sump S of the clutch housing 258 that the lubricant fluid L willattain when the vehicle 10 is not being operated and is disposed on flatand level ground. The main portion 322 can extend around thecircumference of the second wall 288 between the ends 324, 326 and abovethe static lubricant level 328. In the example provided, the staticlubricant level 328 is below a horizontal center line 330 of the clutchhousing 258 that intersects the second axis 240 and is parallel to theground (not shown) when the vehicle 10 is on level ground. In theexample provided, the ends 324, 326 are disposed between the staticlubricant level 328 and the center line 330.

Optionally, the clutch housing 258 can define one or more channels 332.The channels 332 can have a helical or arcuate shape that extendsradially inward from the oil pocket 320 to allow a portion of thelubricant fluid L in the oil pocket 320 to be drained via one or more ofthe channels 332. The channels 332 can direct a portion of the lubricantfluid L that is received into the oil pocket 320 to other structures orcomponents, such as a bearing 334 that supports the outer clutch platecarrier 260 for rotation in the clutch housing 258, a bushing 336 thatsupports output shaft 218 within the clutch housing 258, and/or thefirst and second clutch plates 264, 266, for example. The channels 332can be disposed in the second wall 288 above the static lubricant level328. The channels 332 can have an inlet end 338 and an outlet end 340.The inlet end 338 can open into the main portion 322 and generally facecircumferentially toward end 324. The outlet end 340 can be radiallyinward of the inlet end 338. The channels 332 can extend in an arcuateor helical path from the inlet end 338 to the outlet end 340. While thechannels 332 are shown as open channels, open to the second cavity 280,the channels 332 can alternatively be closed conduits open at the inletend 338 and outlet end 340. The outlet end 340 can be configured todirect lubricant fluid L toward the bearing 334, bushing 336, and/ortoward the second annular cavity 310. In the example provided, threechannels 332 are illustrated, though the clutch housing 258 can defineadditional or fewer channels 332. While each of the channels is shown asextending similarly radially inward, the channels 332 can be configuredto extend different distances radially inward such that the respectiveoutlet ends 340 can be configured to transmit the lubricant fluid L todifferent components or locations in the clutch housing 258. In theexample provided, each inlet end 338 is circumferentially between theends 324, 326 of the oil pocket 320, and each inlet end 338 is above thecenter line 330 of the clutch housing 258.

With additional reference to FIGS. 6 and 7, FIG. 6 depicts the lubricantfluid L in the second clutch 48 when the vehicle 10 is at rest, whileFIG. 7 depicts the lubricant fluid L in the second clutch 48 when thevehicle 10 is moving and the second clutch 48 is not being operated(i.e., the second clutch 48 is not transmitting rotary power). Duringoperation of the vehicle 10 in both the two-wheel drive and four-wheeldrive modes, the outer clutch plate carrier 260 can rotate in arotational direction 342 (FIG. 5) within the clutch housing 258 andthrough the lubricant fluid L in the clutch sump S. Some of thelubricant fluid L in the clutch sump S can cling to the outer clutchplate carrier 260 as it rotates through the lubricant fluid L in theclutch sump S and centrifugal force can sling or direct some of theclinging lubricant fluid L off the outer clutch plate carrier 260 towardthe inner bore surface 292 of the clutch housing 258.

The bore 290 can be sized with a clearance that facilitates axiallubricant fluid L flow in an axial direction 344 (i.e., parallel to therotational axis of the outer clutch plate carrier 260) toward the secondwall 288 of the clutch housing 258. In this regard, lubricant fluid Lthat clings to the outer clutch plate carrier 260 or which passes inradially through the first and second clutch plates 264, 266 and theouter clutch plate carrier 260 can be received into a fourth annularcavity 346 between the inner bore surface 292 and the outer clutch platecarrier 260. The lubricant fluid L in the fourth annular cavity 346 cantravel axially in the fourth annular cavity 346 in the direction 344toward the oil pocket 320. The rotation of the outer clutch platecarrier 260 in the rotational direction 342 will cause the lubricantfluid L to travel in the oil pocket 320 in the rotational direction 342and consequently, lubricant fluid L will tend to migrate into thechannels 332. In the particular example provided, a first portion of thelubricant fluid L in the channels 332 is employed to feed lubricantfluid L to the bearing 334 and the bushing 336, while a second portionof the lubricant fluid L in the channels 332 is directed inwardly to thesecond annular cavity 310 through the through-holes 318 in the outerclutch plate carrier 260. As shown in FIG. 7, when the vehicle 10 ismoving and the second clutch 48 is not being operated, a portion of thelubricant fluid L is removed from the clutch sump S and held in the oilpocket 320, out of the rotating path of the outer clutch plate carrier260.

The reduction of the total amount of lubricant fluid L that the outerclutch plate carrier 260 rotates through can decrease the drag, or spinlosses on the rear drive module 50. Additionally, by redistributing someof the lubricant fluid L from the clutch sump S to other locations, the“paddling effect” can be reduced. Furthermore, the channels 332 candirect some of the lubricant fluid L held in the oil pocket 320 towardother components to lubricate the other components. Specifically, bydirecting some of the lubricant fluid L into the second annular cavity310, the lubricant fluid L can pass through the lubrication holes 312 tolubricate the first and second clutch plates 264, 266.

When the second clutch 48 is operated to transmit rotational power, boththe outer and inner clutch plate carriers 260, 262 can rotate about thesecond axis 240. The lubricant fluid L can be distributed and directedby the rotation of the outer and inner clutch plate carriers 260, 262similar to when the second clutch 48 is not operated. Additionally, someof the lubricant fluid L directed into the second and third annularcavities 310, 314 can cling to the inner clutch plate carrier 262 andthe rotation of the inner clutch plate carrier 262 can cause some of thelubricant fluid L in the second and third annular cavities 310, 314 topass through the lubrication holes 312 into the first annular cavity 308to lubricate the first and second clutch plates 264, 266.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

What is claimed is:
 1. A torque transfer device comprising: a housinghaving an end wall and defining a shaft bore and a central cavity, theshaft bore extending through the end wall, the central cavity beingdisposed about the shaft bore and being bounded on one axial side by theend wall; and a clutch having a first clutch member, the first clutchmember being received in the central cavity and rotatable relative tothe housing about a rotational axis; wherein a portion of the centralcavity forms a lubricant sump that is configured to hold a predeterminedquantity of lubricant through which at least a portion of the clutchrotates when the torque transfer device is transmitting rotary power;wherein a groove is formed into the end wall of the housing at aperiphery of the central cavity, wherein the groove does not intersectthe sump when the housing is positioned in a predetermined positionabout the rotational axis, and wherein a portion of the first clutchmember and a portion of the groove overlap in a radial direction.
 2. Thetorque transfer device of claim 1, further comprising a bearing mountedto the housing concentric with the shaft bore, and wherein a channel isformed in the end wall, the channel having an outlet end that is influid communication with the bearing.
 3. The torque transfer device ofclaim 2, wherein the channel is arcuate in shape.
 4. The torque transferdevice of claim 2, wherein the channel has a spiral shape.
 5. The torquetransfer device of claim 2, wherein the channel has an inlet end that iscoupled in fluid communication to the groove.
 6. The torque transferdevice of claim 2, wherein a hole is formed through the first clutchmember, the hole being positioned in a radial direction so as to sweepacross the channel when the first clutch member rotates about therotational axis relative to the housing, the hole in the first clutchmember being configured to receive lubricant therethrough when the firstclutch member rotates during operation of the torque transfer device. 7.The torque transfer device of claim 1, wherein the groove is shaped asan annular segment.
 8. The torque transfer device of claim 1, whereinthe clutch is a friction clutch.
 9. The torque transfer device of claim1, further comprising a thrust bearing disposed between the end wall andthe first clutch member, the thrust bearing being radially inward of thegroove.
 10. The torque transfer device of claim 1, wherein the housingcomprises an annular wall that is fixedly coupled to the end wall, theannular wall forming a radially outer perimeter of the central cavity,wherein at least a portion of the inside circumferential surface of theannular wall tapers radially outwardly with increasing distance from theend wall.
 11. A torque transfer device comprising: a housing assemblyhaving a first housing member and a second housing member that arecoupled together and cooperate to define a central cavity, the firsthousing member defining an annular piston bore, the second housingmember having an end wall and defining a shaft bore, the shaft boreextending through the end wall, the central cavity being bounded on oneaxial side by the end wall; and a friction clutch having an inputmember, an output member, a plurality of first clutch plates, and aplurality of second clutch plates, the input and output members beingreceived in the central cavity and rotatable about a rotational axis,the first clutch plates being received over and non-rotatably coupled tothe input member, the second clutch plates being received in andnon-rotatably coupled to the output member, the second clutch platesbeing interleaved with the first clutch plates; wherein a portion of thecentral cavity forms a lubricant sump that is configured to hold apredetermined quantity of lubricant through which at least a portion ofthe clutch rotates when the torque transfer device is transmittingrotary power; wherein a groove is formed into the end wall of the secondhousing member at a periphery of the central cavity, wherein the groovedoes not intersect the sump when the housing assembly is positioned in apredetermined position about the rotational axis, and wherein a portionof the output member and a portion of the groove overlap in a radialdirection.
 12. The torque transfer device of claim 11, furthercomprising a bearing mounted to the second housing member concentricwith the shaft bore, and wherein a channel is formed in the end wall,the channel having an outlet end that is in fluid communication with thebearing.
 13. The torque transfer device of claim 12, wherein the channelis arcuate in shape.
 14. The torque transfer device of claim 12, whereinthe channel has a spiral shape.
 15. The torque transfer device of claim12, wherein the channel has an inlet end that is coupled in fluidcommunication to the groove.
 16. The torque transfer device of claim 12,wherein a hole is formed through the output member, the hole beingpositioned in a radial direction so as to sweep across the channel whenthe output member rotates about the rotational axis relative to thehousing assembly, the hole in the output member being configured toreceive lubricant therethrough when the first clutch member rotatesduring operation of the torque transfer device.
 17. The torque transferdevice of claim 11, wherein the groove is shaped as an annular segment.18. The torque transfer device of claim 11, further comprising a thrustbearing disposed between the end wall and the output member, the thrustbearing being radially inward of the groove.
 19. The torque transferdevice of claim 11, wherein the second housing member comprises anannular wall that is fixedly coupled to the end wall, the annular wallforming a radially outer perimeter of the central cavity, wherein atleast a portion of the inside circumferential surface of the annularwall tapers radially outwardly with increasing distance from the endwall.